According to David Finch - WARNING I have no idea who this guy is - SLR joins Equinox, Terenga, and Gold Road, as new additions to GDX, and while New Gold gets dumped. Effective date April 17th (note this was delayed from the usual March rebalance - that much I confirmed independently). Presumably, these changes reflect changes in the NYSE Arca Gold Miners index, which GDX is contractually-obligated to mirror. Unfortunately, getting the NYSE Arca Gold Miners composition requires a fee-based membership, which I have not bought. Note also that, due 4 companies being added to GDX and only 1 dropped, probably the other GDX components will be sold off a bit (these include EVN, NST, and others).
Below is link to Finch's tweet - again, do your own due diligence WRT the information's accuracy; note the rebalance flow estimates.
